At present, a conventional fluoride application (CFA) is used to prevent teeth from demineralization. The process of CFA is to apply colloidal fluoride over a patient's teeth directly and form CaF2 compounds on the teeth. However, many literatures have found that CaF2 compounds can't stay on the teeth for twenty-four hours, so the effect of CFA is limited.
At present, iontophoresis is used as a dental treatment. The principle of iontophoresis is to import electrified medicines into a patient's body by applying an external electric field. Iontophoresis is often used to import electrified medicines into a patient's skin, and the positive effect of iontophoresis has been confirmed.
Iontophoresis has been applied to teeth and imported fluorides into the teeth to prevent the teeth from demineralization. In addition, a previous research reported NaF iontophoresis. NaF iontophoresis imports fluorides into dentinal tubules to produce precipitation of CaF2 by electric voltage. The fluid movement in dentinal tubules is reduced by precipitation of CaF2, thereby the purpose of reducing dentin hypersensitivity can be achieved. However, application of iontophoresis to the teeth still has many problems. For example, the architecture of teeth is very different from that of skin, wherein the skin has more pores and the drug transportation into skin is better.
An electrochemical approach of a current commercial fluoride iontophoresis (FI) device (Pyo-cure, Narcohm, Japan) is based on chronoamperometry (CA). The principle of CA is to provide fixed potentials at different instants, as shown in FIG. 1A, which shows a time-dependent function of potential. The corresponding time function of current is shown in FIG. 1B. As shown in FIG. 1A, when oxidation-reduction substances exist in the system and the potential is fixed at Ea, no oxidation-reduction reaction take place. When the potential is elevated and fixed to Eb, a reduction reaction occurs rapidly, resulting in a rapid decrease of the concentration of the redox substances diffusing to the surface of the working electrode to zero.
The drawbacks of the current commercial FI device include a limited degree of incorporation of fluoride and the failure to import fluoride into inner part of the teeth. They affect the efficiency of the intended demineralization prevention. For example, the duration that fluorine compounds staying in the teeth can't thus be prolonged.
Therefore, there is a need for an improved fluoride iontophoresis to address at least the foregoing issues.